Apparatus for plasma processing

ABSTRACT

A plasma processing apparatus is provided. The plasma processing apparatus can generate a uniform plasma in a processing container to perform a uniform processing on even a large-diameter wafer. The apparatus includes a processing container 4 shaped to be a cylinder with a bottom and accommodating amounting table 10 for mounting a wafer W thereon, a silica plate 8 for covering an upper opening of the processing container 4 in an airtight manner, a microwave supplier 50 for supplying a microwave in TE11 mode and a cylindrical waveguide 52 having one end connected to the microwave supplier 50 to extend toward the silica plate 8 and also having an interior waveguide space. The apparatus further includes a radial waveguide box 54 connected to the other end of the cylindrical waveguide 52. The radial waveguide box 54 is shaped to extend from the other end of the cylindrical waveguide 52 radially outward in the form of a flange and successively extend toward a lid body downward as a sidewall to define an interior waveguide space. The apparatus further includes a disc-shaped slot antenna 60 arranged along the silica plate 8 to cover an opening at the lower end of the radial waveguide box 54 and have a plurality of slots 101, a circularly polarized wave converter 56 disposed in the cylindrical waveguide 52 between the microwave supplier 50 and the radial waveguide box 54 to rotate the TE11-mode microwave provided from the supplier 50 about an axis of the cylindrical waveguide 52 and send the rotating microwave to the radial waveguide box 54.

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a plasma processing apparatusutilizing a microwave.

BACKGROUND OF THE INVENTION

[0002] Conventionally, there is known a plasma processing apparatuswhich includes a flat antenna, as shown in FIG. 18.

[0003] This plasma processing apparatus 71 comprises a processingcontainer 73 generally shaped to be cylindrical with a bottom and asilica plate 75 formed on the ceiling part of the processing container73 in an airtight manner thereby to define a closed processing space Sin the processing container 73. Accommodated in the processing container73 is a mounting table 77 on which a semiconductor wafer W is mounted.This mounting table 77 is connected to a bias high-frequency powersource 79 through power lines. Further, a gas nozzle 81 is arranged inthe sidewall of the processing container 73, for introducing a processgas into the container. The processing container 73 is also provided, ona bottom thereof, with exhaust ports 85 connected with a not-shownvacuum pump.

[0004] On the other hand, a flat antenna member 87 is arranged on thetop of the silica plate 75 sealing up the upside of the processingcontainer 73. The flat antenna member 87 is constituted as a bottomplate of a radial waveguide box 89 consisting of a low and disc-shapedhollow cylindrical container. The flat antenna member 87 is attached toa top surface of the silica plate 75. A coaxial waveguide 93 has itsouter tube 93A connected to the center of an upper face of thedisc-shaped radial waveguide box 89. The coaxial waveguide 93 is alsoconnected, at the other end, with a microwave generator 91. In thecoaxial waveguide 93, an inside cable 93B is connected to the center ofthe disc-shaped antenna member 87.

[0005] The disc-shaped antenna member 87 is made from a copper platehaving a number of slits 95 formed therein. Further, in the radialwaveguide box 89, a dielectric material 97 of predetermined dielectricconstant is accommodated to shorten the wavelength of a microwavethereby accomplishing a short guide wavelength.

[0006] With the above structure, a microwave generated in the microwavegenerator 91 is propagated in the coaxial waveguide 93 and successivelydispersed in the radial waveguide box 89 in the radial direction. Then,the microwave is discharged downward from the slits 95 of the antennamember 87 thereby to form a plasma in the processing container 73.

[0007] However, since cables inside the coaxial waveguide are easy to beheated in the above processing apparatus 71, such an overheatingoperation may cause an abnormal discharging of electricity in theapparatus. In order to prevent the occurrence of abnormal discharging,it is necessary to provide the “so-slender” inside cable with a coolingmechanism. However, this countermeasure would cause the structure of theapparatus to be complicated with an excessive increase in manufacturingcost. Additionally, since the countermeasure requires a supportingstructure for the inside cable, a new problem arises in that it mighttake a great deal of time to adjust an impedance accompanied by theprovision of the supporting structure.

[0008] Further, due to the generation of uneven electric field formedbelow the flat antenna member 87, the processing apparatus 71 has aproblem of producing an uneven treatment on the wafer W. In detail, anelectric field emitted downward from the slits 95 of the flat antennamember 87 is reflected on an inner wall of the processing container 73to produce an uneven electric field in the processing container. Thus,the above processing apparatus betrays an uneven treatment in processingwafers, especially, large-diameter wafers.

[0009] In order to solve the above-mentioned problems, the object of thepresent invention is to provide a plasma processing apparatus which iscapable of prevention of heat-generation of the cable inside the coaxialwaveguide and which can form a uniform electromagnetic field in theprocessing container.

DISCLOSURE OF THE INVENTION

[0010] The first feature of the present invention resides in a plasmaprocessing apparatus which comprises:

[0011] a processing container shaped to be a cylinder with a bottom, theprocessing container having, inside thereof, a mounting table formounting an object to be processed thereon;

[0012] a lid body made of a dielectric material to cover an upperopening of the processing container;

[0013] a microwave supplier for supplying a microwave;

[0014] a cylindrical waveguide having one end connected to the microwavesupplier, the cylindrical waveguide being formed so as to extend fromthe microwave supplier toward the lid body thereby defining a waveguidespace in the cylindrical waveguide;

[0015] a radial waveguide box connected to the other end of thecylindrical waveguide and also formed so as to extend from the other endof the cylindrical waveguide radially outward in form of a flange andsuccessively extend downward therefrom in form of a sidewall, the radialwaveguide box defining another waveguide space therein; and

[0016] a slot antenna arranged along the lid body to cover a loweropening of the radial waveguide box, the slot antenna having a pluralityof slots formed therein.

[0017] With the above constitution, it becomes unnecessary to considerthe heat-generation of cables inside the coaxial waveguide and alsopossible to establish a uniform electromagnetic field in the processingcontainer.

[0018] The second feature of the present invention resides in that theslot antenna is provided, at its part opposing an opening of the otherend of the cylindrical waveguide, with a bump projecting toward thecylindrical waveguide inside the radial waveguide box. With thisarrangement, it is possible to accomplish both introduction andpropagation of a microwave from the cylindrical waveguide into theradial waveguide box effectively.

[0019] The third feature of the present invention resides in that thebump is shaped to be generally conical.

[0020] The fourth feature of the present invention resides in that themicrowave to be propagated from the microwave supplier to the radialwaveguide box through the cylindrical waveguide box is identical to amicrowave in TM01 mode.

[0021] The fifth feature of the present invention resides in that themicrowave to be propagated from the microwave supplier to the radialwaveguide box through the cylindrical waveguide box is identical to amicrowave in TE11 mode.

[0022] The sixth feature of the present invention resides in that theplasma processing apparatus further comprises a circularly-polarizedwave converter which is arranged in the cylindrical waveguide betweenthe microwave supplier and the radial waveguide box to rotate themicrowave in TE11 mode about an axis of the cylindrical waveguidethereby transmitting a resulting circularly-polarized wave to the radialwaveguide box. With the structure mentioned above, it is possible tomake an electromagnetic field in the processing container uniform,thereby preventing an unevenness in producing a plasma.

[0023] The seventh feature of the present invention resides in that theslot antenna is a radiation type of antenna.

[0024] The eighth feature of the present invention resides in that theslots of the slot antenna are arranged coaxially.

[0025] The ninth feature of the present invention resides in that theslots of the slot antenna are arranged spirally.

[0026] The tenth feature of the present invention resides in that theslot antenna is a leak type of antenna.

[0027] The eleventh feature of the present invention resides in that theslots of the slot antenna are arranged coaxially.

[0028] The twelfth feature of the present invention resides in that theslots of the slot antenna are arranged spirally.

[0029] The thirteenth feature of the present invention resides in thatthe slots of the slot antenna are arranged on a periphery of a polygon.

[0030] The fourteenth feature of the present invention resides in thatthe slots of the slot antenna are arranged on radiation lines.

[0031] The fifteenth feature of the present invention resides in that aperiphery between the slot antenna and the processing container has aabsorbing member arranged to absorb a high frequency wave.

[0032] The sixteenth feature of the present invention resides in thatthe slot antenna is held by struts each made of a dielectric material.With this structure, it is possible to produce a uniform plasma.

[0033] The seventeenth feature of the present invention resides in thatan interior of the radial waveguide box is filled up with a dielectricmaterial. With this structure, it is possible to prevent a deformationof the slot antenna.

[0034] The eighteenth feature of the present invention resides in thatan outer periphery inside the radial waveguide box has a absorbingmember arranged to absorb a high frequency wave.

[0035] The nineteenth feature of the present invention resides in thatthe plasma processing apparatus further comprises, between the microwavesupplier and the cylindrical waveguide:

[0036] a rectangular waveguide extending from the microwave supplier;

[0037] a circular-and-rectangular converter arranged between therectangular waveguide and the cylindrical waveguide; and

[0038] a cylindrical dummy load having its one end connected to thecylindrical waveguide between the circular-andrectangular converter andthe circularly-polarized wave converter, the other end of thecylindrical dummy load having a microwave absorber.

[0039] The twentieth feature of the present invention resides in thatthe dummy load is provided, at its connecting part with the cylindricalwaveguide, with a partition wall which separates an interior of thecylindrical waveguide and an interior of the dummy load and has a slitformed to be parallel with an axial direction of the cylindricalwaveguide.

[0040] The twenty-first feature of the present invention resides in thatthe plasma processing apparatus further comprises a rod-shaped reflectorarranged in the waveguide between the cylindrical waveguide and thecircular-and-rectangular converter, the rod-shaped reflector consistingof a conductor bridged in a direction substantially perpendicular to anaxis of the cylindrical waveguide and substantially perpendicular to anextending direction of the dummy load.

[0041] The twenty-second feature of the present invention resides inthat the reflector is a plate body along a plane containing the axis ofthe cylindrical waveguide.

[0042] The twenty-third feature of the present invention resides in thatan axis of the dummy load is arranged in a position apart from thereflector toward the circularly-polarized wave converter by a quarter ofguide wavelength of a standing wave reflected by the reflector.

[0043] The twenty-fourth feature of the present invention resides inthat the plasma processing apparatus further comprises a tuner arrangedin the cylindrical waveguide between the circularly-polarized wave andthe radial waveguide box to adjust an impedance in the cylindricalwaveguide thereby to reflect a microwave, which has been returned byreflection of the radial waveguide box, toward the radial waveguide box.

[0044] The twenty-fifth feature of the present invention resides in thatthe tuner comprises:

[0045] a plurality of stubs projecting from an inner circumferentialwall of the cylindrical waveguide inwardly in a radial directionthereof, with respective adjustable projecting amounts;

[0046] a stub driver for driving the stubs in the radial direction;

[0047] a detector arranged inside the cylindrical waveguide between thestubs and the circularly-polarized converter to detect an intensity ofelectromagnetic field of a microwave in the cylindrical waveguide; and

[0048] a controller for driving the stub driver on a basis of theintensity of electromagnetic field of the microwave detected by thedetector thereby to change respective positions of the stubs in theradial direction for adjustment of an impedance, the controller forcontrolling the microwave, which has been returned from the part of theradial waveguide box, so as to reflect toward the radial waveguide box.

[0049] The twenty-sixth feature of the present invention resides in thatthe stubs are complete in twelve stubs which are arranged on an innercircumferential face of the cylindrical waveguide and which consist offour stubs arranged at regular intervals in a circumferential directionof the cylindrical waveguide for each level and also lined three deepalong an axial direction of the cylindrical waveguide.

[0050] The twenty-seventh feature of the present invention resides in aplasma processing method for a plasma processing apparatus. In thismethod, the plasma processing apparatus includes: a processing containeraccommodating an object to be processed therein and having an upperopening covered by a lid body made of a dielectric material; a microwavesupplier for supplying a microwave; a cylindrical waveguide having oneend connected to the microwave supplier, the cylindrical waveguide beingformed so as to extend from the microwave supplier toward the lid bodythereby defining a waveguide space in the cylindrical waveguide; aradial waveguide box connected to the other end of the cylindricalwaveguide and also formed so as to extend from the other end of thecylindrical waveguide radially outward and successively extend downwardtherefrom in form of a sidewall, the radial waveguide box defininganother waveguide space therein; a slot antenna adapted so as to cover alower opening of the radial waveguide box; and a circularly-polarizedwave converter for rotating a microwave in TE11 mode supplied from themicrowave supplier about an axis of the cylindrical waveguide therebytransmitting the microwave as a circularly-polarized wave to the radialwaveguide box. This plasma processing method comprises the steps of:

[0051] rotating the microwave in TE11 mode supplied from the microwavesupplier about the axis of the cylindrical waveguide therebytransmitting the microwave as the circularly-polarized wave to theradial waveguide box;

[0052] monitoring a microwave which has been reflected by the part ofthe radial waveguide box and subsequently returned therefrom;

[0053] tuning the so-reflected microwave on a basis of a result at themonitoring step; and

[0054] producing a uniform plasma in the processing container by thetuning step.

BRIEF DESCRIPTION OF THE DRAWINGS

[0055]FIG. 1 is a longitudinal sectional view showing a plasmaprocessing apparatus in accordance with the first embodiment of thepresent invention;

[0056]FIG. 2 is a sectional view taken along a line II-II of FIG. 1;

[0057]FIG. 3 is a view showing one example of a radiation type slotantenna;

[0058]FIG. 4 is a view showing another example of the radiation typeslot antenna;

[0059]FIG. 5 is a view showing one example of a leak type slot antenna;

[0060]FIG. 6 is a view showing another example of the leak type slotantenna;

[0061]FIG. 7 is a view showing a further example of the leak type slotantenna;

[0062]FIG. 8 is a view showing a further example of the leak type slotantenna;

[0063]FIG. 9 is a sectional view showing the propagation state of amicrowave in TE mode at a connecting part between a cylindricalwaveguide and a disc-shaped radial waveguide box;

[0064]FIG. 10 is a plan view showing a condition that the microwave inTE mode is being propagated;

[0065]FIG. 11 is a diagram for explanation of a problem to be solved bythe second embodiment of the present invention;

[0066]FIG. 12 is a partially-cutaway plan view showing the plasmaprocessing apparatus in accordance with the second embodiment of thepresent invention;

[0067]FIG. 13 is a partially-cutaway side view showing the plasmaprocessing apparatus in accordance with the second embodiment of thepresent invention;

[0068]FIG. 14 is a view showing the function of a dummy load of theplasma processing apparatus shown in FIG. 12;

[0069]FIG. 15 is a view showing the distribution of an ionic saturatedcurrent in a condition that the dummy load does not function in theplasma processing apparatus shown in FIG. 12;

[0070]FIG. 16 is a view showing the distribution of an ionic saturatedcurrent in a condition that the dummy load functions in the plasmaprocessing apparatus shown in FIG. 12;

[0071]FIG. 17 is a partially-cutaway plan view showing the plasmaprocessing apparatus in accordance with the third embodiment of thepresent invention; and

[0072]FIG. 18 is a longitudinal sectional view of the conventionalplasma processing apparatus.

BEST MODE OF EMBODIMENTS OF THE INVENTION

[0073] With reference to attached drawings, a plasma processingapparatus in accordance with one embodiment of the present inventionwill be described below, in detail. FIG. 1 is a sectional view of anexample of the plasma processing apparatus of the present invention.FIG. 2 is a view showing a section of a circularly polarized waveconverter, taken along a line II-II of FIG. 1.

[0074] Although the plasma processing apparatus is embodied by a plasmaetching apparatus in this embodiment, it is a matter of course that thepresent invention is not limited to this example only. The plasmaetching apparatus 2 includes a processing container 4 having itssidewall and bottom made of a conductive material, such as aluminum, andshaped to be a cylinder with a bottom as a whole. The ceiling part ofthe processing container 4 is opened. A silica plate 8 having athickness to endure a vacuum pressure is disposed on the opened ceilingpart through a sealing member 6, such as O-ring, in an airtight manner,thereby to form a sealed processing space S in the container.

[0075] In the processing container 4, a mounting table 10 isaccommodated to mount a semiconductor wafer W as an object to beprocessed, on a top surface of the table. Using “Alumite-processed”aluminum, the mounting table 10 is formed in the shape of a generalcolumn which is provided, at a center thereof, with a flattenedprojection. The lower part of the mounting table 10 is supported by asupporting table 12 shaped to be columnar by aluminum as well. Thesupporting table 12 is mounted on the bottom of the processing container4 through an insulator 14.

[0076] On the top surface of the mounting table 10, there are providedan electrostatic chuck (not shown) and a clamping mechanism (not shown)for holding a wafer. The mounting table 10 is connected to a matchingbox 18 and a “bias” high-frequency power source 20. The supporting table12 for supporting the mounting table 10 is provided with a coolingjacket 22 for passage of a cooling water for cooling a wafer at theplasma processing.

[0077] Arranged in the sidewall of the processing container 4 is a gasnozzle 24 which is made of a silica pipe, for introducing an etching gasas the processing gas into the container. The nozzle 24 is connected toa processing-gas source 32 through a gas supply path 26 interposing amass-flow controller 28 and a closing valve 30 therein.

[0078] On the periphery of the sidewall of the processing container 4,there is provided, along the circumferential direction, a magnetic-fieldgenerator 34, such as electromagnetic coil and permanent magnet, whichgenerates a magnetic field in the processing space S to confine aso-produced plasma therein. Note, the magnetic-field generator 34 is notalways required to produce a plasma and therefore, the generator may beeliminated in the modification.

[0079] The processing container 4 is also provided, at a bottom thereof,with exhaust ports 36 which are connected to a not-shown vacuum pump forallowing an interior of the processing container 4 to be evacuated intoa designated pressure.

[0080] A microwave generator 50 is arranged above the silica plate 8 ofthe processing container 4. A cylindrical waveguide 52 is connected tothe microwave generator 50 so that a microwave generated by thegenerator 50 can be propagated in the waveguide 52. As to the microwave,there can be employed microwaves in TM01 mode and TE11 mode.Particularly, it is desirable to use a circularly polarized microwave inTE11 mode in view of preventing an unevenness in producing a plasma. Theoperation in case of using the microwave in TE11 mode will be describedas follows.

[0081] A radial waveguide box 54 is connected to the cylindricalwaveguide 52. A circularly-polarized wave converter 56 is disposedbetween the radial waveguide box 54 and the microwave generator 50.Although there exist various kinds of circularly-polarized waveconverters, this embodiment employs a circularly-polarized waveconverter that, as shown in FIG. 2, two metallic columnar projections 58are arranged on an inside wall of the cylindrical waveguide so as toface each other in one or plural pairs in the axial direction. Thecolumnar projections 58 are positioned in respective directions at anangle of 45 with a main direction of an electric field of the TE11-modemicrowave propagated from the microwave generator. Thiscircularly-polarized wave converter rotates the main direction of anelectric field of the TE11-mode microwave from the microwave generator50, about the axis of the cylindrical waveguide as a rotational center.

[0082] Being connected to the lower end of the cylindrical waveguide 52,the radial waveguide box 54 has a flange part 56 extending from thelower end of the cylindrical waveguide 52 outward in the radialdirection and a wall part 58 extending from the outer margin of theflange part 56 downward toward the silica plate 8. On the lower openingof the radial waveguide box 54, a slot antenna 60 in the form of adisc-shaped copper plate is fitted so as to overlay the above openingthereby to define a waveguide space therein. The slot antenna 60 is heldby struts 130 of dielectric materials projecting from the flange part 56downward, thereby preventing a deformation of the antenna.

[0083] This disc-shaped slot antenna 60, which is a type of radiationantenna, has a structure similar to that of a “microwave” flat antennato be used for communication and produces a plasma by a microwaveradiated from the antenna plate. In the slot antenna 60, the interval ofslots is set to λg/2 or λg (λg: guide wavelength) both exhibiting a highefficiency in radiating a microwave. In this embodiment, as shown inFIG. 3, many pairs of slots 101 in general V-shaped arrangement areformed on concentric circles on the slot antenna. Note, as the antennaof radiation type, there may be recommended a slot antenna 105 wheremany pairs of slots 103 in general V-shaped arrangement are formed in aspiral manner, as shown in FIG. 4.

[0084] Alternatively, the slot antenna used in this apparatus may berepresented by a leak type of antenna that produces a plasma by amicrowave leaking out of the antenna. The interval of slots in thisleak-type antenna is normally from λ/3 to λ/40 or thereabout, which isnarrower than that of the radiation-type antenna, as shown with a slotantenna 107 of FIG. 5 where a number of slots 109 are arranged onconcentric circles. As to the leak-type slot antenna, there exist a slotantenna 111 of FIG. 6 having a number of slots 113 formed in spiral, aslot antenna 115 of FIG. 7 having a number of slots 117 formed inhexagonal and a slot antenna 119 of FIG. 8 having a number of slots 121formed in radial.

[0085] Inside the radial waveguide box 54, a metallic bump 64 is formedat the center of the disc-shaped antenna member 60. This bump 64 isshaped so as to be a cone projecting toward the lower opening of thecylindrical waveguide 52 and also having a spherical tip. Owing to thisprovision of the bump 64, it is possible to guide and propagate anelectromagnetic field, which has been propagated in the cylindricalwaveguide 52, into the radial waveguide box 54.

[0086] A space defined by the radial waveguide box 54 and thedisc-shaped antenna member 60 is filled by a dielectric material 66. Inthe circumferential part between the slot antenna 60 and the processingcontainer 4, an absorber 68 for absorbing a high-frequency wave isarranged to prevent the reflection of an electromagnetic field. Such anabsorber may be arranged in an outer circumferential part inside theradial waveguide box 54.

[0087] Next, the operation of the above-constructed apparatus of theembodiment will be described. First, a semiconductor wafer W istransported through a not-shown gate valve by a transfer arm andaccommodated in the processing container 4. Then, by moving lifter pins(not shown) up and down, the wafer W is mounted on a mounting surface ofthe mounting table 10. Next, an etching gas whose flow rate iscontrolled is supplied from the gas nozzle 24 while a pressure in theprocessing container 4 is maintained to a designated pressure. At thesame time, a microwave generated from the microwave generator 50 isintroduced into the processing space S to produce a plasma for etching.During this operation, the application of a bias high-frequency power onthe mounting table 10 allows an electrically-negative potential to begenerated on the mounting table 10, thereby allowing ions to beextracted from the plasma effectively. Note, the magnetic fieldgenerator 34 on the sidewall of the processing container 4 is providedto generate a magnetic field for confining the plasma in the container.Therefore, it is possible to produce a plasma by the microwave from thedisc-shaped antenna member 60, irrespective of the presence of themagnetic field generator.

[0088] In the above-mentioned structure, the “TE11 mode” microwavegenerated from the microwave generator 50 reaches thecircularly-polarized wave converter 56 through the cylindrical waveguide52. There, the “TE11 mode” microwave is rotated about the axis of thecylindrical waveguide 52 and reaches the waveguide's connecting partwith the radial waveguide box 54. At this connecting part, as shown inFIG. 9, a horizontal electric field E of the “TE11 mode” microwave isdivided into left and right by the bump 64 and subsequently propagatedtoward the periphery of the radial waveguide box while changing thedirection of the electric field vertically. Hereat, the so-dividedelectric fields are deviated from each other by an angle of 180°, onboth sides of the bump 64. Then, the microwave propagated toward theperiphery generates an electromagnetic field in the processing spacebeneath the disc-shaped slot antenna 60, so that the plasma is producedby the above electromagnetic field.

[0089] Hereat, since the microwave propagated in the cylindricalwaveguide 52 is in the TE mode, an electric field F generated in theprocessing container 4 through the disc-shaped slot antenna 60 isunevenly and strongly distributed in the direction of the electric fieldE in the cylindrical waveguide 52, as shown in FIG. 10. Despite that,since the microwave propagated in the cylindrical waveguide 52 rotatesabout the axis of the cylindrical waveguide, the intensive electricfield (parts) F is rotated as well. Therefore, in the processing space Sbelow the disc-shaped slot antenna 60, an intensity of theelectromagnetic field is so equalized that an even and uniform plasmacan be produced over a wide range in the space. Accordingly, whenprocessing even a large-diameter wafer, it is possible to accomplish auniform processing in the surface of the wafer.

[0090] As mentioned above, this plasma processing apparatus includes theprocessing container 4 shaped to be a cylinder with a bottom and having,inside thereof, the mounting table 10 for mounting the wafer W thereon,the silica plate 8 for covering the upper opening of the processingcontainer 4 in an airtight manner, the microwave supplier 50 forsupplying the “TE11 mode” microwave, the cylindrical waveguide 52 havingone end connected to the microwave supplier 50 to extend toward thesilica plate 8 and also defining a waveguide space therein, the radialwaveguide box 54 connected to the other end of the cylindrical waveguide52 and also shaped to extend from the other end of the cylindricalwaveguide 52 radially outward thereby forming a flange and successivelyextend toward the lid body downward thereby forming a sidewall anddefining a waveguide space therein, the disc-shaped slot antenna 60arranged along the silica plate 8 to cover the lower opening of theradial waveguide box 54 and having the plural slots 101, and thecircularly-polarized wave converter 56 disposed in the cylindricalwaveguide 52 between the microwave supplier 50 and the radial waveguidebox 54 to rotate the “TE11 mode” microwave provided from the microwavesupplier 50 about the axis of the cylindrical waveguide 52 and furthersend the rotating microwave to the radial waveguide box 54. Therefore,it is possible to rotate the “TE11 mode” microwave, which has beenpropagated in the cylindrical waveguide 52, about the axis of thecylindrical waveguide and also possible to cause the microwave havingits phase reversed to be propagated toward the periphery of the radialwaveguide box 54. Accordingly, in the processing space S below thedisc-shaped slot antenna 60, it is possible to make an intensity ofplasma even and uniform over a wide range in the space. Thus, whenprocessing even a large-diameter wafer, it is possible to accomplish auniform processing in the surface of the wafer. Additionally, it ispossible to prevent cables inside the coaxial waveguide from beingheated.

[0091] Although this plasma processing apparatus is capable of producinga uniform plasma in the processing space as mentioned above, there hasbeen found a slight unevenness in the distribution of plasma inaccordance with a more detailed measurement. It is believed that thisphenomenon comes from the following reasons.

[0092] That is, as shown in FIG. 11, a “TE11 mode” traveling wave 155falling in an upper cylindrical waveguide 151 is rotated in a clockwisedirection by the circularly-polarized wave converter 56 and falls in alower cylindrical waveguide 153 while rotating as shown with a referencenumeral 157. This microwave 157 is divided into left and right by thebump 64 and directs toward the periphery of the radial waveguide box 54,so that the microwave is propagated into the processing space throughthe disc-shaped slot antenna 60. Nevertheless, this microwave isextremely partially reflected by the slot antenna 60 in the processingcontainer, so that the so-reflected microwave is propagated upward inthe lower cylindrical waveguide 153 while retracing in the oppositeroute, as shown with a reference numeral 159. When this microwavereaches the upper cylindrical waveguide 151 through thecircularly-polarized wave converter 56, it becomes a “TE11 mode”microwave that does not rotate, as shown with a reference numeral 161.This microwave is reflected on a waveguide's connecting part 173 with arectangular waveguide 171, so that the phase of microwave is reversed.Then, the so-reflected microwave as a traveling wave, falls in thecylindrical waveguide 151, as shown with a reference numeral 163. Next,by passing through the circularly-polarized wave converter 56 again, themicrowave is rotated and falls in the lower cylindrical waveguide 153,as shown with a reference numeral 165. Here, due to a plane ofpolarization different from that of the traveling wave 155 by an angleof 90°, the microwave 165 rotates in the counter-clockwise directionagainst the rotating direction of the microwave 157. In this way, it issupposed that the distribution of microwave becomes uneven because themicrowave 165 in the counter-clockwise direction interferes with theproper microwave 157 in the clockwise direction.

[0093] Provided to improve such a drawback is a plasma processingapparatus 200 of the second embodiment which is shown in FIGS. 12 to 14.

[0094] In FIG. 12, reference numeral 201 designates a rectangularwaveguide. The rectangular waveguide 201 is connected to a not-shownmicrowave generator. The rectangular waveguide 201 is bent at a cornerpart 203 by an angle of 90° and further connected to acircular-and-rectangular converter 205. A cylindrical waveguide 207 isconnected to the circular-and-rectangular converter 205. Below thecylindrical waveguide 207, there is provided a circularly-polarized waveconverter 209 which rotates a microwave in TE11 mode about an axis ofthe converter. A flange-shaped radial waveguide box 211 is connected tothe lower part of the circularly-polarized wave converter 209 succeedingthe cylindrical waveguide 207, allowing a microwave to be propagatedfrom the slot antenna on a lower face of the radial waveguide box 211into the processing container.

[0095] In the above plasma processing apparatus, a dummy load 215 in theform of a rectangular cylinder is arranged on the upper part of thecylindrical waveguide 207, in the vicinity of a waveguide's connectingpart 213 with the circular-and-rectangular converter 205. This dummyload 215 extends in a direction perpendicular to the axis of thecylindrical waveguide 207, at a position of a distance L away from theconnecting part between the cylindrical waveguide 207 and thecircular-and-rectangular converter 205. Hereat, it is desirable thatwhen a microwave propagated in the cylindrical waveguide 207 in theopposite direction is reflected at the connecting part 213 thereby toform a standing wave, the distance L becomes equal to a quarter of awavelength of the standing wave and further, the dummy load 215 has itsaxis positioned at an antinode of the standing wave. The dummy load 215is provided, at an end thereof, with a microwave absorber 217. Forexample, as shown in FIG. 14, the microwave absorber 217 may be formedto be a cone storing water therein, allowing a microwave to be absorbedby the cone. The dummy load 215 is provided, in its part close to thecylindrical waveguide 207, with a shutter 219 which makes it possible tointerrupt the absorption of microwave by the dummy load 215 optionally.At the connecting part of the dummy load 215 with the cylindricalwaveguide 207, a shield plate 221 is provided with a slit 223 inparallel with the axis of the cylindrical waveguide 207. The slit 223 isformed to have, for example, a length of 50 to 120 mm and a width of 2to 20 mm. Additionally, at the connecting part 213, a rod-shapedreflecting plate 225 is arranged so as to be perpendicular to the axisof the cylindrical waveguide and also a projecting direction of thedummy load 215. The reflecting plate 225 is made of conductor and shapedin the form of a plate in a direction along a plane containing the axisof the cylindrical waveguide 207.

[0096] In the above-mentioned structure of the present invention, when amicrowave, which has be propagated from the radial waveguide box 211 inthe opposite direction, passes through the circularly-polarized waveconverter 209 and reaches the connecting part 213 between thecylindrical waveguide 207 and the circular-and-rectangular converter205, the microwave reflects at the connecting part 213 without enteringinto the rectangular waveguide 201. Particularly, since the plasmaprocessing apparatus 200 has the reflecting plate 225 arranged at theconnecting part 213, the microwave is reflected at the plate 225 therebyto form a standing wave C having a node at the reflecting plate 225, asshown in FIG. 14. Since the axis of the dummy load 215, i.e. a center ofthe slit is positioned apart from the connecting part 213 by a quarterof a wavelength of the standing wave, the antinode of the standing waveC coincides with the center of the slit 223. Then, the standing wave ispropagated into the dummy load 215 through the slit 223 and subsequentlyabsorbed in the absorber 217.

[0097] In this way, since the microwave reflected from the radialwaveguide box 211 is absorbed in the dummy load, there is no possibilitythat the microwave is propagated toward the radial waveguide box 211again. That is, since the uniformity of the microwave propagated fromthe radial waveguide box 211 into the processing container is notdisturbed, it is possible to maintain the uniformity of plasma in theprocessing container at a higher level.

[0098]FIGS. 15 and 16 are respective diagrams showing experimentalresults of the above-mentioned effect. These figures are obtained bymeasuring the intensity of saturated ionic currents on the mountingtable. The measurement has been carried out at a center R1 of themounting table and also in respective angular positions in thecircumferential direction of respective circumferences of radii R2, R3and R4 (the outermost circumference). The measuring results aredesignated in the form of graphs.

[0099] In these figures, FIG. 15 illustrates the measured saturatedionic currents on condition of closing the shutter 219 in the dummy load215, that is, an inactivated condition of the dummy load 215. From thisfigure, it will be understood that, in the state of the inactivateddummy load 215, the saturated ionic currents on the mounting table varywidely in the circumferential direction and additionally, such atendency is remarkable in the outer peripheral position particularly.

[0100] To the contrary, FIG. 16 shows a situation to open the shutter219, in other words, an activated condition of the dummy load 215. Fromthis figure, it will be understood that the saturated ionic currents onthe mounting table represent respective constant values in all cases ofboth circumferential direction and radial direction and therefore, aninfluence due to the reflection of microwave is reduced remarkably.

[0101] Referring to FIG. 17, we describe a plasma processing apparatus300 in accordance with the third embodiment whose effect is similar tothat of the second embodiment.

[0102] In this figure, as similar to FIG. 12, a reference numeral 201designates a rectangular waveguide, 203 a corner part, 205 acircular-and-rectangular converter, 207 a cylindrical waveguide, 209circularly-polarized wave converters, and 211 a radial waveguide box.

[0103] The cylindrical waveguide 207 is provided, at a lower partthereof, with a tuner 311. This tuner 311 has a plurality of stubs 313formed to project from the inner circumferential face of the lower partof the cylindrical waveguide 207 inward in the radial direction. Byprojecting into the cylindrical waveguide 207, these stubs 313 operateto change an impedance thereby to drive the microwave, which has beenreflected by the radial waveguide box 211, back to the same box 211. Thenumber of stubs 313 is twelve in total: four stubs each at regularintervals of an angle of 90° in the circumferential direction; and threepairs of stubs at regular intervals in the axial direction of thecylindrical waveguide. For these stubs 313, there are provided stubdrivers 315 which drive the stubs 313 to the radial direction,respectively.

[0104] Detectors 317 are arranged on the inner circumferential face ofthe cylindrical waveguide 207 between the stubs 313 and thecircularly-polarized wave converters 209. The detectors 317 are providedto detect the microwave that has been reflected by the radial waveguidebox 211. The number of detectors 317 is twelve in total: four detectorseach at regular intervals of an angle of 90° in the circumferentialdirection; and three pairs of detectors at regular intervals of λg/8 inthe axial direction.

[0105] The apparatus further includes a controller 319. Based on theintensity of an electromagnetic field of microwave measured by thedetectors 317, the controller 319 drives the stub drivers 315 to changethe positions of the stubs 313 in the radial direction, therebyadjusting an impedance in tuning.

[0106] With the constitution mentioned above, the microwave propagatedfrom the radial waveguide box 211 in the opposite direction is detectedby the detectors 317 and the so-obtained measurement is transmitted tothe controller 319. Then, on a basis of the intensity of theelectromagnetic field of microwave measured by the detectors 317, thecontroller 319 calculates the positions of the stubs 313 in the radialdirection required to reflect the microwave, which has been returnedfrom the part of the radial waveguide box 211, toward the same box 211again. Continuously, the controller 319 outputs a drive command of thestubs 313 to the stub drivers 315. In accordance with the drive command,each of the stub drivers 315 changes the radial-directional position ofthe stub 313 to adjust the impedance for tuning, whereby the returnedmicrowave is reflected toward the radial waveguide box 211.

[0107] In this way, according to the plasma processing apparatus 300,since the reflection wave from the radial waveguide box is tuned andreflected in front of the circularly-polarized wave converter 209, therotating direction of the circularly-polarized wave is not reversed.Accordingly, it is possible to propagate a uniform microwave from theslot antenna, thereby accomplishing a uniform plasma processing.

[0108] Next, the matching operation for circularly-polarized wave bythis tuner will be described.

[0109] As to the circularly-polarized wave in TE11 mode in the circularwaveguide, the rectangular waveguide is replaced by the circularwaveguide thereby to produce the “TE11 mode” circularly-polarized waveby the circularly-polarized wave generator having a phase plate etc.arranged in the part of the circular waveguide.

[0110] It is noted that the reflection wave from the load of thecircular waveguide travels in the opposite direction of the travelingwave and rotates in the same direction as the traveling wave.

[0111] Therefore, in the part of the circular waveguide, a standing waveproduced by the reflection wave is identical to a standing wave of theTE11 mode (not a circularly-polarized wave) in the axial direction ofthe waveguide at a position of a constant angle.

[0112] As to the angular direction, since a standing wave is generatedin the circumference, it is also possible to detect the standing wave inthis direction.

[0113] As to the detection of the standing wave, there are providedthree to five styluses at regular intervals of λg/8 of the guidewavelength, so that the detector detects a microwave detected by thestyluses (three to five styluses at regular intervals of an angle of 45°in the circumferential direction).

[0114] For example, in case of detecting the standing wave by fourstyluses, the absolute value of voltage is calculated by the followingexpression.

|V|=|Vi|{square root}{square root over ( )}[1+|Γ|²+2|Γ| cos (θ−2βl)]

[0115] Under the square-law detection, respective voltages of thedetectors #1, #2, #3, #4 are as follows:

V ₁ =K|Vi| ²(1+|Γ|²+2|Γ| cos θ)

V ₂ =K|Vi| ²(1+|Γ|²−2|Γ| sin θ)

V ₃ =K|Vi| ²(1+|Γ|²−2|Γ| cos θ)

V ₄ =K|Vi| ²(1+|Γ|²+2|Γ| sin θ)

[0116] Therefore, there are established the following expressions.

V ₁ −V ₃=4K|Vi| ²|Γ| cos θ

V ₄ −V ₂=4K|Vi| ²|Γ| sin θ

[0117] Since this signal contains the information of both reflectioncoefficient |Γ| and phase θ, if normalizing the member of 4K|Vi|² in theabove equations, then the values of |Γ| cos θ, |Γ| sin θ are calculatedto allow an impedance of load to be calculated.

[0118] Alternatively, in case of detecting the standing wave by threestyluses, there are established the following expressions:

V ₁ =K|Vi| ²(1+|²+2|Γ| cos θ)

V ₂ =K|Vi| ²(1+|²−2|Γ| sin θ)

V ₃ =K|Vi| ²(1+|²−2|Γ| cos θ)

V ₁ −V ₃=4K|Vi| ²|Γ|² cos θ

[0119] [(V ₁ +V ₃)/2]−V ₂=4K|Vi| ²|Γ|sin θ

[0120] Similarly, the values of |Γ| cos θ, |Γ| sin θ are calculated toobtain the impedance of load in calculation.

[0121] Note, even if there are provided, at regular intervals of anangle of 45° in the circumferential direction of the circular waveguide,three or more detection terminals in place of the detectors in the axialdirection, the impedance of load can be calculated similarly.

[0122] That is, the use of either three to four detectors in the axialdirection or four detectors in the circumferential direction employingallows an automatic matching operation to be realized.

[0123] If only calculating the positions of three stubs arranged atintervals of (λg/8) to (λg/4) (recommended) by using the so-calculatedimpedance of load by means of a microcomputer and subsequently adjustingthe positions of three stubs, then a matching can be accomplished.

[0124] When the stubs of plural number (e.g. four) are arranged in thecircumferential direction, the circumferential balance for circularpolarized wave is so improved as to allow of automatic matching againstthe large reflection of load.

[0125] Note, although the plasma processing apparatus 200 equipped withthe dummy load 215 and the plasma processing apparatus 300 equipped withthe tuner 311 have been described independently of each other in theabove-mentioned embodiments, the present invention is applicable to aplasma processing apparatus equipped with both of dummy load and tuner,of course.

[0126] Additionally, although the plasma processing apparatus is appliedto the plasma etching apparatus in common with the above embodiments,the present invention may be applied to other processes, for example,film-deposition process, process to improve properties of film, etc.

[0127] According to the present invention, the plasma processingapparatus includes the processing container shaped to be a cylinder witha bottom, the processing container having, inside thereof, the mountingtable for mounting an object to be processed thereon, the lid body madeof a dielectric material to cover an upper opening of the processingcontainer, the microwave supplier for supplying a microwave, thecylindrical waveguide having one end connected to the microwavesupplier, the cylindrical waveguide being formed so as to extend fromthe microwave supplier toward the lid body thereby defining a waveguidespace in the cylindrical waveguide, the radial waveguide box connectedto the other end of the cylindrical waveguide and also formed so as toextend from the other end of the cylindrical waveguide radially outwardin form of a flange and successively extend downward therefrom in formof a sidewall, the radial waveguide box defining another waveguide spacetherein and the slot antenna arranged along the lid body to cover alower opening of the radial waveguide box, the slot antenna having aplurality of slots formed therein. Therefore, it is possible to preventan inside cable from generating heat, which might be caused in using acoaxial waveguide. Furthermore, it is possible to produce a uniformplasma in the processing container, thereby allowing an even treatmentto be applied on even a large-diameter wafer.

What is claimed is:
 1. A plasma processing apparatus comprising: aprocessing container shaped to be a cylinder with a bottom, theprocessing container having, inside thereof, a mounting table formounting an object to be processed thereon; a lid body made of adielectric material to cover an upper opening of the processingcontainer; a microwave supplier for supplying a microwave; a cylindricalwaveguide having one end connected to the microwave supplier, thecylindrical waveguide being formed so as to extend from the microwavesupplier toward the lid body thereby defining a waveguide space in thecylindrical waveguide; a radial waveguide box connected to the other endof the cylindrical waveguide and also formed so as to extend from theother end of the cylindrical waveguide radially outward in form of aflange and successively extend downward therefrom in form of a sidewall,the radial waveguide box defining another waveguide space therein; and aslot antenna arranged along the lid body to cover a lower opening of theradial waveguide box, the slot antenna having a plurality of slotsformed therein.
 2. A plasma processing apparatus as claimed in claim 1,wherein the slot antenna is provided, at its part opposing an opening ofthe other end of the cylindrical waveguide, with a bump projectingtoward the cylindrical waveguide inside the radial waveguide box.
 3. Aplasma processing apparatus as claimed in claim 2, wherein the bump isshaped to be generally conical.
 4. A plasma processing apparatus asclaimed in any one of claims 1-3, wherein the microwave to be propagatedfrom the microwave supplier to the radial waveguide box through thecylindrical waveguide box is identical to a microwave in TM01 mode.
 5. Aplasma processing apparatus as claimed in any one of claims 1-3, whereinthe microwave to be propagated from the microwave supplier to the radialwaveguide box through the cylindrical waveguide box is identical to amicrowave in TE11 mode.
 6. A plasma processing apparatus as claimed inclaim 5, further comprising a circularly-polarized wave converterarranged in the cylindrical waveguide between the microwave supplier andthe radial waveguide box to rotate the microwave in TE11 mode about anaxis of the cylindrical waveguide thereby transmitting a resultingcircularly-polarized wave to the radial waveguide box.
 7. A plasmaprocessing apparatus as claimed in any one of claims 1-6, wherein theslot antenna is a radiation type of antenna.
 8. A plasma processingapparatus as claimed in claim 7, wherein the slots of the slot antennaare arranged coaxially.
 9. A plasma processing apparatus as claimed inclaim 7, wherein the slots of the slot antenna are arranged spirally.10. A plasma processing apparatus as claimed in any one of claims 1-6,wherein the slot antenna is a leak type of antenna.
 11. A plasmaprocessing apparatus as claimed in claim 10, wherein the slots of theslot antenna are arranged coaxially.
 12. A plasma processing apparatusas claimed in claim 10 wherein the slots of the slot antenna arearranged spirally.
 13. A plasma processing apparatus as claimed in claim10 wherein the slots of the slot antenna are arranged on a periphery ofa polygon.
 14. A plasma processing apparatus as claimed in claim 10wherein the slots of the slot antenna are arranged on radiation lines.15. A plasma processing apparatus as claimed in any one of claims 1-14,wherein a periphery between the slot antenna and the processingcontainer has a absorbing member arranged to absorb a high frequencywave.
 16. A plasma processing apparatus as claimed in any one of claims1-15, wherein the slot antenna is held by struts each made of adielectric material.
 17. A plasma processing apparatus as claimed in anyone of claims 1-16, wherein an interior of the radial waveguide box isfilled up with a dielectric material.
 18. A plasma processing apparatusas claimed in any one of claims 1-18, wherein an outer periphery insidethe radial waveguide box has a absorbing member arranged to absorb ahigh frequency wave.
 19. A plasma processing apparatus as claimed inclaim 6, further comprising, between the microwave supplier and thecylindrical waveguide: a rectangular waveguide extending from themicrowave supplier; a circular-and-rectangular converter arrangedbetween the rectangular waveguide and the cylindrical waveguide; and acylindrical dummy load having its one end connected to the cylindricalwaveguide between the circular-and-rectangular converter and thecircularly-polarized wave converter, the other end of the cylindricaldummy load having a microwave absorber.
 20. A plasma processingapparatus as claimed in claim 19, wherein the dummy load is provided, atits connecting part with the cylindrical waveguide, with a partitionwall which separates an interior of the cylindrical waveguide and aninterior of the dummy load and has a slit formed to be parallel with anaxial direction of the cylindrical waveguide.
 21. A plasma processingapparatus as claimed in claim 19, further comprising a rod-shapedreflector arranged in the waveguide between the cylindrical waveguideand the circular-and-rectangular converter, the rod-shaped reflectorconsisting of a conductor bridged in a direction substantiallyperpendicular to an axis of the cylindrical waveguide and substantiallyperpendicular to an extending direction of the dummy load.
 22. A plasmaprocessing apparatus as claimed in claim 21, wherein the reflector is aplate body along a plane containing the axis of the cylindricalwaveguide.
 23. A plasma processing apparatus as claimed in claim 19,wherein an axis of the dummy load is arranged in a position apart fromthe reflector toward the circularly-polarized wave converter by aquarter of guide wavelength of a standing wave reflected by thereflector.
 24. A plasma processing apparatus as claimed in claim 6,further comprising a tuner arranged in the cylindrical waveguide betweenthe circularly-polarized wave and the radial waveguide box to adjust animpedance in the cylindrical waveguide thereby to reflect a microwave,which has been returned by reflection of the radial waveguide box,toward the radial waveguide box.
 25. A plasma processing apparatus asclaimed in claim 24, wherein the tuner comprises: a plurality of stubsprojecting from an inner circumferential wall of the cylindricalwaveguide inwardly in a radial direction thereof, with respectiveadjustable projecting amounts; a stub driver for driving the stubs inthe radial direction; a detector arranged inside the cylindricalwaveguide between the stubs and the circularly-polarized converter todetect an intensity of electromagnetic field of a microwave in thecylindrical waveguide; and a controller for driving the stub driver on abasis of the intensity of electromagnetic field of the microwavedetected by the detector thereby to change respective positions of thestubs in the radial direction for adjustment of an impedance, thecontroller for controlling the microwave, which has been returned fromthe part of the radial waveguide box, so as to reflect toward the radialwaveguide box.
 26. A plasma processing apparatus as claimed in claim 25,wherein the stubs are complete in twelve stubs which are arranged on aninner circumferential face of the cylindrical waveguide and whichconsist of four stubs arranged at regular intervals in a circumferentialdirection of the cylindrical waveguide for each level and also linedthree deep along an axial direction of the cylindrical waveguide.
 27. Aplasma processing method for a plasma processing apparatus including: aprocessing container accommodating an object to be processed therein andhaving an upper opening covered by a lid body made of a dielectricmaterial; a microwave supplier for supplying a microwave; a cylindricalwaveguide having one end connected to the microwave supplier, thecylindrical waveguide being formed so as to extend from the microwavesupplier toward the lid body thereby defining a waveguide space in thecylindrical waveguide; a radial waveguide box connected to the other endof the cylindrical waveguide and also formed so as to extend from theother end of the cylindrical waveguide radially outward and successivelyextend downward therefrom in form of a sidewall, the radial waveguidebox defining another waveguide space therein; a slot antenna adapted soas to cover a lower opening of the radial waveguide box; and acircularly-polarized wave converter for rotating a microwave in TE11mode supplied from the microwave supplier about an axis of thecylindrical waveguide thereby transmitting the microwave as acircularly-polarized wave to the radial waveguide box; the plasmaprocessing method comprising the steps of: rotating the microwave inTE11 mode supplied from the microwave supplier about the axis of thecylindrical waveguide thereby transmitting the microwave as thecircularly-polarized wave to the radial waveguide box; monitoring amicrowave which has been reflected by the part of the radial waveguidebox and subsequently returned therefrom; tuning the so-reflectedmicrowave on a basis of a result at the monitoring step; and producing auniform plasma in the processing container by the tuning step.